Zen V4, updated

In 2009, Penultimate Zen aka Zen V4 was my first solid state build. I used the parts that were available, did not know much about making it work well, and did not have test instruments beyond a cheap multimeter. Also, I did not have a preamplifier to work with it or speakers sensitive enough to enjoy its 25W. As a result, the amplifier turned out not quite satisfactory and for two years has been gathering dust and my wife's complaints. I was thinking about scrapping it and reusing the enclosure for something more useful. Instead, I reworked it.

I removed one of the two power transformers (moving from dual mono to stereo configuration), replaced my original dodgy Chinese PSU filter caps with Mundorf M-Lytic HC, replaced internal low voltage wiring with thick speaker wire, reconfigured grounding (so it is finally safe!) and installed balanced inputs with input transformers. What a change in sound! With my Exposure CD player, B1 clone preamp and Heresy III speakers, the amp provides enjoyable listening to Placido Domingo's arias. It also has (some) bass now, which was sorely missing before. Frankly, I did not expect such a change from apparently minor amendments.

Also, I installed a commercial soft start module, which also provides a pushbutton on/off and works with PTC thermistors to protect the amplifier from overheating.

I do have a more radical idea for this amp, so there will be another post.